Feed pellets for ruminants

ABSTRACT

The present invention aims to provide feedstuffs for ruminants with high nutritional value and high digestion efficiency.According to the present invention, feed pellets for ruminants containing a kraft pulp derived from a lignocellulosic material are provided, wherein the kraft pulp has a Canadian standard freeness of less than 400 ml.

TECHNICAL FIELD

The present invention relates to feedstuffs for ruminants and processes for preparing them.

BACKGROUND ART

Generally in the field of livestock farming, concentrate feedstuffs with high nutritional value are often used in combination with roughage feedstuffs such as forages in order to increase milk production or to increase weight gain in livestock.

Concentrate feedstuffs are rich in easily digestible carbohydrates (starch and the like) such as maize, cereal grains and soybean, while roughage feedstuffs mainly include dried forages (hay, straw), early harvested and fermented (i.e., ensiled) forages and the like.

Ruminants can ingest and digest roughage feedstuffs because they have a rumen (first stomach). The rumen occupies the largest volume among the multiple stomachs of ruminants, and contains a rich diversity of microorganisms (i.e., ruminal microorganisms) capable of degrading hard-to-digest polysaccharides such as celluloses and hemicelluloses in roughage feedstuffs (ruminal fermentation).

However, celluloses and hemicelluloses in roughage feedstuffs are often bound to lignins and exist as lignin-cellulose complexes and lignin-hemicellulose complexes, respectively. Such complexes may not be degraded sufficiently by ruminal fermentation, and therefore, roughage feedstuffs had the drawback that they tended to have insufficient feed efficiency. Moreover, an increase in undigested materials was considered to be environmentally undesirable because it leads to an increase in feces.

In addition, the supply of roughage feedstuffs is unstable because it is susceptible to the harvest yield or crop yield of forages. Especially, Japan mostly relies on imported roughage feedstuffs, which are generally subject to significant price variation or may be difficult to import depending on circumstances in exporting countries, thereby putting a squeeze on livestock farmers.

Thus, it would be desirable to provide inexpensive and stably available feedstuffs for ruminants with high feed efficiency that can substitute for forages.

In this connection, concentrate feedstuffs rich in easily digestible carbohydrates (starch) are typically combined with roughage feedstuffs to increase nutrient levels in feedstuffs. To maintain milk production in dairy livestock or to maintain weight gain in livestock for meat, feed intake must also be increased because the rate of increase in the energy required to increase milk production or weight gain exceeds the rate of increase in feed intake. However, carbohydrates such as starch in concentrate feedstuffs may cause a sudden drop of pH in the first stomach (rumen), resulting in ruminal acidosis. Ruminal acidosis is one of ruminant diseases caused by a sudden intake of cereal grains, concentrate feedstuffs, fruits or the like rich in carbohydrates. Ruminal acidosis is caused by the growth of gram-positive lactate-producing bacteria, especially Streptococcus bovis and microorganisms of the genus Lactobacillus, which results in abnormal accumulation of lactic acid or volatile fatty acids (VFAs) in the rumen, whereby the pH in the rumen drops (to pH 5 or less). This results in decreased numbers or disappearance of protozoa and certain types of bacteria in the rumen. Especially, acute acidosis is very critical because it leads to congestion of the rumen or dehydration (a shift of a lot of body fluids into the stomach due to an increase in the osmotic pressure in the stomach lumen), and eventually coma or death.

To prevent ruminal acidosis, it is important to avoid sudden changes in feed formulations, thereby stabilizing ruminal fermentation and reducing pH variations. It is also important to provide feedstuffs that stimulate adequate rumination to promote salivation because saliva contains sodium bicarbonate contributing to pH adjustment. However, feedstuffs with reduced nutritional value for preventing ruminal acidosis raise concerns of decreased milk production due to energy shortage.

Feedstuffs for preventing ruminal acidosis are disclosed in PTL 1, which describes livestock feedstuffs obtained by applying a high impact force to a wood raw material to break up it into microparticles. As for pelletized feedstuffs, PTL 2 proposes to prepare feedstuffs by pelletizing food processing residues. PTL 3 also describes pelletizing a lignocellulosic biomass to prepare a feedstuff for ruminants (JPA 2013-518880). Further, PTL4 describes pelletizing a kraft pulp having a kappa number of 90 or less to prepare a feedstuff for ruminants.

CITATION LIST Patent Literature

-   PTL 1: JPA2011-083281 -   PTL 2: JPA1998-75719 -   PTL 3: International Publication WO2011/097075 -   PTL 4: JPA2015-198653

SUMMARY OF INVENTION Technical Problem

It is generally known that high-fiber roughage feedstuffs such as forages contribute little to the improvement of the fat content of milk or the marbling degree because they have low fermentability, and therefore low nutritional value.

On the other hand, it is contemplated that feedstuffs should be provided in the form of pellets or the like for easy handling of the feedstuffs. However, too soft pellets are difficult for ruminants to eat as a matter of course but also sometimes they are broken or give off dust during transportation. Especially, it is difficult to prepare hard pellets from extensively delignified pulps such as kraft pulps because they contain low levels of thermoplastic lignins.

Thus, the present invention aims to provide feedstuffs for ruminants with high nutritional value and high digestion efficiency as well as little likelihood that ruminal acidosis will occur or various metabolic disorders or reproductive diseases will occur before and after delivery as it happens when higher proportions of concentrate feedstuffs are given.

Solution to Problem

As a result of careful studies about the problems described above, the inventors of the present invention accomplished the present invention on the basis of the finding that feedstuffs with high nutritional value and high digestion efficiency can be prepared by incorporating a kraft pulp having a Canadian standard freeness adjusted to less than 400 ml.

-   (1) A feed pellet for ruminants containing a kraft pulp derived from     a lignocellulosic material, wherein the kraft pulp has a Canadian     standard freeness of less than 400 ml. -   (2) The feed pellet of (1) wherein the lignocellulosic material     comprises a wood material. -   (3) The feed pellet of (1) or (2) wherein the kraft pulp has a kappa     number of 5 to 15. -   (4) The feed pellet of any one of (1) to (3) wherein the pellet has     a mechanical durability of 97.5 % by mass or more and a diameter of     3 to 10 mm. -   (5) A process for preparing the feed pellet of any one of (1) to     (4), comprising pressing/compressing a kraft pulp having a moisture     content of 15 to 35 % by mass to pelletize it.

Advantageous Effects of Invention

The present invention makes it possible to obtain feedstuffs with high digestion efficiency, which are highly preferred by ruminants and assume the form of easy-to-handle pellets. Further, the feed pellets for ruminants according to the present invention can be stably supplied because they can be prepared from lignocellulosic raw materials such as wood.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a photograph showing the appearance of feed pellets prepared in Experiment 1 (Sample 1).

DESCRIPTION OF EMBODIMENTS Feed Pellets

The feed pellets for ruminants according to the present invention are applied to ruminants. Ruminants include, for example, cattle such as dairy cattle and beef cattle, sheep, goats and the like. The time at which the feedstuffs of the present invention are fed to the ruminants, i.e., the age, size, health condition or the like of the ruminants of interest is not specifically limited, and they may be applied, for example, from suckling calves to adult cattle.

The feed pellets of the present invention have a hardness enough to resist breakage and powdering during transportation, and preferably have a mechanical durability of 97.5% or more (as determined according to “6.5 Testing Methods of Mechanical Durability” defined in the Wood Pellet Quality Standards). The mechanical durability is an indication of the unlikelihood that pellets would break, and refers to the percentage of the mass of pellets that did not break into powder when a given amount of mechanical impact was applied. In preferred embodiments, the feed pellets of the present invention have a mechanical durability of 98.0% or more, more preferably 99.0% or more.

The feed pellets according to the present invention can be prepared by pelleting a raw material including a kraft pulp by a known method. The shape and size of the feed pellets according to the present invention are not specifically limited, but the diameter of each pellet can be, for example, 2 to 20 mm, preferably 3 to 10 mm. The length of each pellet is preferably, for example, 1 to 200 mm, more preferably 5 to 80 mm, still more preferably 10 to 60 mm, or may be 15 to 45 mm.

Pelleting can be performed by compression molding using a known apparatus. The apparatus for compression molding is not specifically limited, but preferred examples include briquetters (from Kitagawa Corporation), ring die pellet mills (from CPM), and flat die pellet mills (from DALTON CORPORATION), for example.

The feed pellets of the present invention contain a bleached or unbleached kraft pulp, preferably 10% by mass or more, more preferably 50% by mass or more, still more preferably 80% by mass or more of a kraft pulp, or they may consist solely of a kraft pulp. They may also contain other feed ingredients, as appropriate. The kraft pulp preferably has been oxygen-dclignified, and preferably has a kappa number of 30 or less, more preferably has a kappa number of 5 to 15, or may have a kappa number of 7 to 13. If the kappa number is 30 or less, ruminants’ preference is improved.

The feed pellets of the present invention contain a kraft pulp (KP), which can be used in combination with other pulps prepared by known pulping processes. For example, both mechanical and chemical pulps can be applied. Mechanical pulps include groundwood pulp (GP), refiner groundwood pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP) and the like. Chemical pulps include kraft pulp (KP), dissolving kraft pulp (DKP), sulfite pulp (SP), dissolving sulfite pulp (DSP) and the like. Further, both bleached and unbleached pulps can be used. Among them, preferred are oxygen-delignified chemical pulps, bleached chemical pulps and the like. More preferred are pulps or kraft pulps having a kappa number of 5 or more and less than 15, and especially preferred are oxygen-delignified kraft pulps having a kappa number of 5 or more and less than 15.

In the feedstuffs for ruminants according to the present invention, the pulp may consist of a single pulp or may be a mixture of multiple pulps. For example, a mixture of two or more of chemical pulps (hardwood kraft pulps, softwood kraft pulps, hardwood dissolving kraft pulps, softwood dissolving kraft pulps), or mechanical pulps (groundwood pulps, refiner groundwood pulps, thermomechanical pulps, chemithermomechanical pulps) derived from different sources or prepared by different processes may be used.

Mechanical pulps can contain undisintegrated lumps by preparing them without undergoing any screening process after grinding (in cases of groundwood pulps) or after refining (in cases of refiner groundwood pulps, thermomechanical pulps, and chemithermomechanical pulps).

Wood raw materials that can be used include, for example, hardwoods, softwoods, trysting trees, bamboo, kenaf, bagas and empty fruit brunches obtained after palm oil extraction. Specifically, examples of hardwoods include Fagus crenata, Tilia japonica, Betula platyphylla, Populus, Eucalyptus, Acacia, oaks, Acer pictum subsp. mono, Kalopanax septemlobus, elms, Paulownia tomentosa, Mangolia obovata, willows, Kalopanax pictus Nakai, Quercus phillyraeoides, Quercus serrata, Quercus acutissima, Aesculus turbinata, Zelkova serrata, Betula grossa, Cornus controversa, Fraxinus lanuginosa f. serrata and the like. Examples of softwoods include Cryptomeria japonica, Picea jezoensis, Larix kaempferi, Pinus thunbergii, Abies Sachalinensis, Pinus parviflora var. parviflora, Taxus cuspidata, Thuja standishii, Picea torano, Picea alcokiana, Podocarpus macrophyllus, Abies firma, Chamaecyparis pisifera, Pseudotsugajaponica, Thujopsis dolabrata, Thujopsis dolabrata var. hondae, Tsuga sieboldii, Tsuga diversifolia, Chamaecyparis obtusa, Taxus cuspidata, Cephalotaxus harringtonia, Picea jezoensis var. hondoensis, yellow cedar (Cupressus nootkatensis), Lawson’s cypress (Chamaecyparis lawsoniana), Douglas fir (Pseudotsuga menziesii), Sitka spruce (Picea sitchensis), Pinus radiata, eastern spruce, eastern white pine, western larch, western fir, western hemlock, Larix occidentalis and the like.

Kraft Pulp

The feed pellets according to the present invention contain a kraft pulp obtained by kraft cooking of a lignocellulosic raw material, especially preferably contain a wood-derived kraft pulp. Especially in the present invention, feed pellets that are easily digestible in the rumen of ruminants can be prepared by using a kraft pulp having a Canadian standard freeness (CSF) of less than 400 ml. In preferred embodiments, the Canadian standard freeness of the kraft pulp used in the present invention is 385 ml or less, or may be 350 ml or less or 300 ml or less. Typically, the Canadian standard freeness of the kraft pulp can be reduced by processing with a known beater such as a double disc refiner, a single disc refiner, a conical refiner or a PFI mill or the like.

In the present invention, the average fiber length of the kraft pulp is not specifically limited. In preferred embodiments, the average fiber length can be less than 0.68 mm, or may be less than 0.65 mm in cases of hardwood kraft pulps, while the average fiber length can be less than 1.50 mm, or may be less than 1.45 mm in cases of softwood kraft pulps. Feed pellets with high digestion efficiency can be prepared by decreasing the average fiber length. The average fiber length of the kraft pulp can be controlled by suitably formulating the lignocellulosic raw material because kraft pulps having a longer fiber length can generally be obtained by kraft cooking of wood species having a longer fiber length. For example, pulps having a longer average fiber length can be obtained by preparing a kraft pulp with high proportions of softwood materials because the fiber length of softwoods is often longer than the fiber length of hardwoods.

In preferred embodiments, the kraft pulp used in the present invention has a breaking length of 7.0 km or more, more preferably 8.0 km or more, still more preferably 9.0 km or more. The breaking length refers to the length of a paper strip vertically suspended from one end when it breaks of its own weight, and typically expressed in km. As used herein, the breaking length of a kraft pulp refers to the breaking length of a laboratory sheet having a basis weight of 60 g/m² prepared from the pulp, as determined according to JIS P 8113. In the present invention, feed pellets are preferably prepared from a kraft pulp having a longer breaking length, because they can provide feedstuffs with high digestion efficiency in ruminants. The upper limit of the breaking length is not specifically defined, but preferably can be 20 km or less, or may be 15 km or less.

For preparing a kraft pulp from wood chips, the wood chips are fed into a digester together with a cooking liquor and subjected to kraft cooking. Alternatively, they may be subjected to a modified kraft cooking process such as MCC, EMCC, ITC, Lo-solids or the like process. Further, the digester system is not specifically limited, including one-vessel liquor phase, one-vessel steam/liquor phase, two-vessel liquor/steam phase, two-vessel liquor phase or the like system. Thus, the step of impregnating wood chips with an aqueous alkaline solution and holding them described herein may be provided separately from conventional equipment or sites intended for impregnation treatments with cooking liquors. Preferably, the cooked unbleached pulp is washed in a washer such as a diffusion washer after the cooking liquor has been extracted.

The kraft cooking process can be performed by feeding wood chips together with a kraft cooking liquor into an autoclave, which is not specifically limited to any shape or size. The ratio of liquor to wood chips can be, for example, 1.0 to 5.0 L/kg, preferably 1.5 to 4.5 L/kg, more preferably 2.0 to 4.0 L/kg.

In the present invention, an alkaline cooking liquor containing a quinone compound may be added to the digester. When an alkaline cooking liquor containing a quinone compound is added, the quinone compound is preferably 0.01 to 1.5% by mass based on the bone dry weight of chips. If the amount of the quinone compound added is less than 0.01% by mass, it is too little to reduce the kappa number of the pulp after cooking so that the relationship between the kappa number and the pulp yield cannot be improved. Moreover, reduction of lumps and reduction in viscosity loss are also insufficient. Even if the amount of the quinone compound added exceeds 1.5% by mass, however, neither further reduction in the kappa number of the pulp after cooking nor improvement in the relationship between the kappa number and the pulp yield is observed.

The quinone compound used is a quinone compound, a hydroquinone compound or a precursor thereof known as the so-called digestion aid, and at least one compound selected from these members can be used. These compounds include, for example, quinone compounds such as anthraquinones, dihydroanthraquinones (e.g., 1,4-dihydroanthraquinone), tetrahydroanthraquinones (e.g., 1,4,4a,9a-tetrahydroanthraquinone, 1,2,3,4-tetrahydroanthraquinone), methylanthraquinones (e.g., 1-methylanthraquinone, 2-methylanthraquinone), methyldihydroanthraquinones (e.g., 2-methyl-1,4-dihydroanthraquinone), and methyltetrahydroanthraquinones (e.g., 1-methyl-1,4,4a,9a-tetrahydroanthraquinone, 2-methyl-1,4,4a,9a-tetrahydroanthraquinone); hydroquinone compounds such as anthrahydroquinones (typically 9, 10-dihydroxyanthracene),methylanthrahydroquinones (e.g., 2-methylanthrahydroquinone),dihydroanthrahydroanthraquinones (e.g., 1,4-dihydro-9,10-dihydroxyanthracene) or alkali metal salts thereof (e.g., the disodium salt of an anthrahydroquinone, the disodium salt of 1,4-dihydro-9,10-dihydroxyanthracene); and precursors thereof such as anthrones, anthranols, methylanthrones, and methylanthranols. These precursors have the potential to be converted into quinone compounds or hydroquinone compounds under cooking conditions.

The cooking liquor preferably has an active alkali charge (AA) of 10 to 35% by mass based on the bone dry weight of wood chips when the wood chips are derived from softwoods. If the active alkali charge is less than 10% by mass, lignins or hemicelluloses are not sufficiently removed, but if it exceeds 35% by mass, the yield decreases or the quality decreases. As used herein, the active alkali charge refers to the total charge of NaOH and Na₂S, expressed as the charge of Na₂O obtained by multiplying the charge of NaOH by 0.775 and the charge of Na₂S by 0.795 to convert them into the corresponding charge of Na₂O. Further, it preferably has a sulfidity in the range of 20 to 35%. In regions having a sulfidity of less than 20%, delignification is poor, the pulp viscosity decreases, and the percentage of lumps increases.

Kraft cooking preferably takes place in the temperature range of 120 to 180° C., more preferably 140 to 160° C. If the temperature is too low, delignification (reduction in kappa number) is insufficient, but if the temperature is too high, the degree of polymerization (viscosity) of celluloses decreases. Further, the cooking time is preferably 60 minutes or more and 600 minutes or less, more preferably 120 minutes or more and 360 minutes or less, wherein the cooking time as used herein refers to a period of time after the cooking temperature reaches the maximum temperature before the temperature begins to drop. If the cooking time is shorter than 60 minutes, pulping does not proceed, but if it exceeds 600 minutes, the pulp production efficiency decreases, and therefore, either case is not preferred.

In the kraft cooking process according to the present invention, the process temperature and the process time can be selected based on the H-factor (Hf). The H-factor is an indicator of the total amount of heat given to a reaction system during cooking and expressed by the equation below. The H-factor is calculated by integration over time from the instant when chips and water are mixed to the end of cooking. The H-factor is preferably 300 to 2000.

Hf = ∫exp (43.20 − 16113/T)dt

wherein T represents the absolute temperature at a given instant.

In the present invention, the unbleached pulp obtained after cooking can be subjected to various treatments, as appropriate. For example, the unbleached pulp obtained after kraft cooking can be subjected to a bleaching process.

The pulp obtained after kraft cooking can be subjected to an oxygen delignification process. The oxygen delignification process used in the present invention can be performed by directly applying a known medium consistency method or high consistency method. Preferably, the medium consistency method is performed at a pulp consistency of 8 to 15% by mass, and the high consistency method is performed at 20 to 35% by mass. Alkalis that can be used in the oxygen delignification process include sodium hydroxide and potassium hydroxide, and oxygen gases that can be used include oxygen from cryogenic separation, oxygen from PSA (Pressure Swing Adsorption), oxygen from VSA (Vacuum Swing Adsorption) and the like.

Reaction conditions for the oxygen delignification process include, but are not specifically limited to, an oxygen pressure of 3 to 9 kg/cm², more preferably 4 to 7 kg/cm², an alkali charge of 0.5 to 4% by mass based on the bone dry weight of pulp, a process temperature of 80 to 140° C., a process time of 20 to 180 minutes, and other known conditions. It should be noted that the oxygen delignification process may be performed multiple times in the present invention. Further, the kraft pulp preferably has a kappa number of 5 to 15 after it has been subjected to the oxygen delignification process or the like.

When the kappa number is desired to be further reduced or the brightness is desired to be further improved, the oxygen-delignified pulp is then sent to, for example, a washing step in which it is washed, and then sent to a multistage bleaching step in which it can be subjected to a multistage bleaching process. The multistage bleaching process in the present invention preferably includes, but not specifically limited to, the use of a known bleaching agent such as an acid (A), chlorine dioxide (D), an alkali (E), oxygen (O), hydrogen peroxide (P), ozone (Z), a peracid or the like in combination with a bleaching aid. For example, a multistage bleaching sequence is preferably used, comprising a first stage using a chlorine dioxide bleaching stage (D) or an ozone bleaching stage (Z), a second stage using an alkali extraction stage (E) or a hydrogen peroxide stage (P), and a third and the subsequent stages using chlorine dioxide or hydrogen peroxide. The number of stages subsequent to the second stage is not specifically limited either, but the total number of stages is preferably at most three or four to ensure energy efficiency, productivity and the like. Further, a chelating agent treatment stage using ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA) or the like may be inserted into the multistage bleaching process.

The feed pellets of the present invention can be fed to ruminants in combination with other feedstuffs. Other feed ingredients include roughage feedstuffs (e.g., forages), concentrate feedstuffs (e.g., cereal grains such as maize and wheat, beans such as soybean), wheat bran, rice bran, soy pulp, proteins, fats, vitamins, minerals and the like as well as additives (preservatives, colorants, perfumes, etc.) and the like. These other feed ingredients may be mixed with wood pulp during compression molding.

The feedstuffs for ruminants according to the present invention preferably have a water content of 15% by mass or less. When the water content is 15% by mass or less, transportability is improved whereby microbial corrosion can be reduced.

Feeding of the Feed Pellets to Ruminants

The feed pellets of the present invention can be fed to ruminants in combination with other feedstuffs. Other feed ingredients include roughage feedstuffs (e.g., forages), concentrate feedstuffs (e.g., cereal grains such as maize and wheat, beans such as soybean), wheat bran, rice bran, soy pulp, proteins, fats, vitamins, minerals and the like as well as additives (preservatives, colorants, perfumes, etc.) and the like. These other feed ingredients may be mixed with wood pulp during compression molding.

The feed pellets for ruminants according to the present invention preferably have a water content (moisture content) of 15% by mass or less. When the water content is 15% by mass or less, transportability is improved whereby microbial corrosion can be reduced. The water content of the feed pellets may be, for example, 1% by mass or more, or may be adjusted to 5% by mass or more.

EXAMPLES

The following examples further illustrate the present invention, but the present invention is not limited to these examples. It should be noted that the concentration and% values as used herein are based on mass unless otherwise specified, and the numerical ranges are described to include their endpoints.

Experiment 1: Preparation of Feed Pellets Using Kraft Pulps as Raw Materials (Samples 1 to 4: LOKPs)

Eucalyptus wood chips having a radius (Φ) of 25.4 mm to 9.5 mm (in an amount equivalent to 300 g on a bone dry basis) were subjected to kraft cooking in an autoclave under the conditions of an active alkali charge of 14%, a sulfidity of 25%, an H-factor of 830, and a liquor-to-wood ratio of 2.5 to give an unbleached hardwood kraft pulp (kappa number: 17.6, ISO brightness: 36.4%).

This unbleached hardwood kraft pulp was washed with tap water and adjusted to a consistency of 10%, and then subjected to oxygen delignification under the conditions of an oxygen charge of 2.1% (based on the bone dry weight of the pulp), and a sodium hydroxide charge of 1.4% (based on the bone dry weight of the pulp) at 100° C. for 60 minutes to give an oxygen-delignified hardwood kraft pulp (LOKP, kappa number: 11.1, ISO brightness: 54.7%).

Further, this unbleached kraft pulp was beaten in a PFI mill (from KUMAGAI RIKI KOGYO Co., Ltd.) (Sample 1: freeness 265 ml, Sample 2: freeness 392 ml, Sample 3: freeness 426 ml, Sample 4: freeness 520 ml).

Then, the oxygen-delignified hardwood kraft pulps (LOKPs) having different freenesses were dehydrated to a moisture content of 30% by weight by using a centrifugal dehydrator (YS-7SSA from lwatsuki Machinery Co., Ltd.), and then processed in a small ring die pellet mill (having a motor power of 30 kw from California Pellet Mill) through die holes having a diameter Φ of 4.8 mm and an effective thickness of 32 mm to prepare feed pellets. The moisture content of the pellets was adjusted by an air stream dryer.

Samples 5 to 8: NOKPs

Chips (having a thickness of about 3 mm) prepared from Cryptomeria japonica wood were screened through a sieve to give Cryptomeria japonica wood chips having a radius (Φ) of 25.4 mm to 9.5 mm. The chips (in an amount equivalent to 300 g on a bone dry basis) were subjected to kraft cooking in an autoclave under the conditions of an active alkali charge of 18.5%, a sulfidity of 25%, an H-factor of 1500, and a liquor-to-wood ratio of 3.2 to give an unbleached softwood kraft pulp (kappa number: 25.5, ISO brightness: 26.3%).

This unbleached softwood kraft pulp was washed with tap water and adjusted to a consistency of 10%, and then subjected to oxygen delignification under the conditions of an oxygen charge of 2.9% (based on the bone dry weight of the pulp), and a sodium hydroxide charge of 2.2% (based on the bone dry weight of the pulp) at 100° C. for 60 minutes to give an oxygen-delignified softwood kraft pulp (NOKP, kappa number: 10.8, ISO brightness: 32.1%).

Further, this unbleached kraft pulp was beaten in a PFI mill (from KUMAGAI RIKI KOGYO Co., Ltd.) (Sample 5: freeness 245 ml, Sample 6: freeness 380 ml, Sample 7: freeness 435 ml, Sample 8: freeness 680 ml).

Then, feed pellets were prepared from the unbleached kraft pulps in the same manner as described for Sample 1 and subjected to various tests.

<Analyses of the Kraft Pulps>

The kraft pulp used for each sample was determined for the Canadian standard freeness (CSF) according to JIS P 8121, the kappa number according to JIS P 8221, and the number average fiber length according to ISO 16065-2. Further, laboratory sheets were prepared according to JIS P 8222: 1998 and determined for the breaking length according to JIS P 8113: 1998.

<Mechanical Durability Test>

The feed pellets described above were evaluated for the mechanical durability of wood pellets according to the “Testing Methods of Mechanical Durability” defined in the Wood Pellet Quality Standards (established Mar. 31, 2011 by Japan Wood Pellet Association). The mechanical durability defined in the Wood Pellet Quality Standards was standardized according to the European Standard EN 15210-1 and refers to the ability of wood pellets to resist powdering when exposed to a mechanical impact. Specifically, the mechanical durability (DU) was determined by the equation below using the pellet durability tester model DT-T (from SANYO TRADING CO., LTD.).

Mechanical durability(%) = m1/m0 × 100

wherein m1: the mass (g) of the sample before tumbling; m0: the mass (g) of the sample after tumbling.

TABLE 1 Sample 1 2 3 4 Properties of pulp Material type - LOKP (Eucalyptus) LOKP (Eucalyptus) LOKP (Eucalyptus) LOKP (Eucalyptus) Freeness ml 265 392 426 520 Fiber length mm 0.63 0.66 0.69 0.71 Breaking length km 7.8 7.1 6.8 2.9 Kappa number 11.1 11.1 11.1 11.1 Moisture content before pelleting % 33.4 26.3 29.3 31.9 Properties of pellets Mechanical durability % 99.3 99.6 99.5 99.3 Diameter mm 4.8 4.8 4.8 4.8 Length mm 36 29 34 31 Moisture content % 12.1 16.3 13.9 15.4

Sample 5 6 7 8 Properties of pulp Material type - NOKP (Cryptomeria) NOKP (Cryptomeria) NOKP (Cryptomeria) NOKP (Cryptomeria) Freeness ml 245 380 435 680 Fiber length mm 1.44 1.46 -1.51 1.98 Breaking length km 9.1 8.9 8.3 3.1 Kappa number 10.8 10.8 10.8 10.8 Moisture content before pelleting % 34.1 32.1 29.9 27.5 Properties of pellets Mechanical durability % 99.5 99.6 99.4 99.3 Diameter mm 4.8 4.8 4.8 4.8 Length mm 21 26 31 35 Moisture content % 15.1 14.9 13.5 14.2

Experiment 2: Feeding to Ruminants (in-Situ Digestion Test)

The digestibility in the rumen was determined by an in situ method (Journal of Dairy Science, vol. 71, pages 2051-2069, 1988, James E. Nocek).

Into the rumen of a test animal (a cow) were inserted polyester bags (#R1020, polyester, 10 cm x 20 cm, average pore diameter 50±15 µm, ANKOM Technology Corp., Fairport, NY, USA) containing each sample weighing 5 g (on an air-dry basis). At 2 hours, 4 hours, 8 hours, 24 hours, 48 hours, 72 hours, and 96 hours after the polyester bags were inserted, they were removed from the rumen, and washed with water, and dried to a constant mass at 60° C. to determine the dry matter weight. The same polyester bags containing each feedstuff were prepared except that they were not inserted into the rumen but simply washed with water, and used as samples at a degradation time of 0 hour. Each sample was measured on three different successive days.

As controls, steam-flaked corn (Sample 9: a concentrate feedstuff available from Nakajima Seibaku Kogyo K.K. as steam-flaked corn) and bermudagrass hay (Sample 10: a roughage feedstuff available from Takeda K.K. as Bermuda hay bales produced in U.S.) were inserted into the rumen of the cow and subjected to the digestion test.

TABLE 2 Sample 1 2 3 4 5 6 7 8 9 Raw material LOKP LOKP LOKP LOKP NOKP NOKP NOKP NOKP Concent Freeness of pulp (ml) 265 392 426 520 245 380 435 680 - Mechanical durability of feed pellets % 99.6 99.5 99.3 99.4 99.6 99.3 99.3 99.5 - In situ dry matter digestibility (%) 0 hr 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 28.6 2 hr 1.1 0.7 0.0 0.0 1.9 0.1 0.0 0.0 40.5 4 hr 6.8 5.6 3.0 2.1 6.9 4.5 2.3 1.7 47.2 8 hr 15.6 13.7 9.1 7.9 15.6 11.6 6.1 4.5 57.2 24 hr 54.7 52.1 41.8 36.3 53.3 45.7 31.2 25.4 77.6 48 hr 90.1 87.2 81.8 77.8 86.1 82.3 73.3 69.1 94.8 72 hr 94.9 94.2 94.0 93.1 88.9 87.5 86.6 83.9 96.9

Experiment 3: Feeding to Ruminants (Feeding Test)

Holstein steers were divided into groups of six animals for each test condition and fed with feedstuffs for six months from 7 months to 12 months of age after birth. Feeding of test feedstuffs included time-restricted feeding of a commercially available formulated feedstuff (available from Kumamoto Dairy Co-Operative Association under the brand name Kumaraku P&F74C) as a concentrate feedstuff and ad libitum feeding of samples. The feed intake by steers (dry matter intake) was calculated by subtracting the remaining amount of the feed (dry matter) from the amount of the feed given (dry matter).

TABLE 3 Sample 1 2 3 4 5 6 7 8 Raw material LOKP LOKP LOKP LOKP NOKP NOKP NOKP NOKP Freeness (ml) 265 392 426 520 245 380 435 680 Mechanical durability of feed pellets % 99.3 99.6 99.5 99.3 99.5 99.6 99.4 99.3 Concentrate feed intake (kg) Months of age 7.5 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 8 5.3 5.3 5.3 5.3 5.3 5.3 5.3 5.3 8.5 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 9 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.3 9.5 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 10 7.4 7.4 7.4 7.4 7.4 7.4 7.4 7.4 10.5 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 11 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 11.5 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 12 9.7 9.7 9.7 9.7 9.7 9.7 9.7 9.6 12.5 9.9 9.9 9.9 9.8 9.9 9.9 9.9 9.7 Total 82.5 82.5 82.5 82.4 82.5 82.5 82.5 82.2 Roughage feed intake (kg) Months of age 7.5 3.5 3.6 3.0 2.9 3.4 3.5 3.2 2.7 8 3.2 3.7 3.1 2.6 3.3 3.1 2.9 3.0 8.5 3.6 3.5 3.0 2.9 3.7 3.4 3.1 3.1 9 4.0 3.8 2.7 3.1 4.2 3.5 3.2 2.7 9.5 3.9 3.9 2.9 2.8 4.3 3.8 3.1 2.7 10 3.9 3.6 2.7 2.4 4.3 3.6 2.9 2.6 10.5 3.6 3.4 2.1 1.9 3.8 3.2 2.6 2.4 11 2.9 3.0 2.3 2.1 3.0 2.9 2.4 2.3 11.5 2.6 2.1 2.0 1.9 2.5 2.6 1.6 1.7 12 2.9 2.4 1.9 1.8 2.7 2.6 1.7 1.7 12.5 2.7 2.4 2.0 1.8 2.8 2.4 1.7 1.5 Total 36.8 35.4 27.7 26.2 38.0 34.6 28.4 26.4

Feed pellets prepared from kraft pulps having a freeness of less than 400 ml exhibited higher digestion rates and higher intakes as compared with feed pellets prepared from pulps having a freeness of 400 ml or more. It seems that pulps having a freeness of less than 400 ml can reduce the decrease in feed intake because they take shorter to saccharify and stay in the rumen for a shorter period of time. The feed pellets of the present invention prepared from kraft pulps having a low freeness seem to be digested more rapidly (at a higher digestion rate) because the kraft pulps have finer fiber ends.

Further, the final digestibilities of the feed pellets according to the present invention were comparable to those of the feed pellets prepared from kraft pulps having a higher freeness and the concentrate feedstuff (Sample 9) and higher than that of the roughage feedstuff (Sample 10). This indicates that the feed pellets according to the present invention are converted into energy with high efficiency.

In addition, the feed pellets according to the present invention seem to contribute to preventing acidosis because they take longer to saccharify than the concentrate feedstuff (Sample 9).

In conclusion, the present invention made it possible to prepare feed pellets for ruminants with high nutritional value capable of reducing the decrease in feed intake. 

1-5. (canceled)
 6. A feed pellet for ruminants containing a kraft pulp derived from a wood material, wherein the kraft pulp has a Canadian standard freeness of less than 400 ml, wherein the wood material comprises hardwoods and/or softwoods, and wherein the pellet has a mechanical durability of 97.5% by mass or more and a water content of 15% by mass or less.
 7. The feed pellet of claim 6, which is prepared by a method comprising the steps of: cooking the wood material under the conditions of H factor being 300 to 2000 to obtain the kraft pulp; beating the kraft pulp using a beater to Canadian Standard Freeness of less than 400 mL; pressing/compressing the kraft pulp having a moisture content of 15 to 35% by mass to obtain the pellet; and then drying the pellet to a water content of less than 15%.
 8. The feed pellet of claim 6, wherein the pellet has a mechanical durability of 98% by mass or more and a diameter of 3 to 10 mm.
 9. The feed pellet of claim 6, wherein the kraft pulp comprises an oxygen-delignified kraft pulp having a kappa number of 5 to
 13. 10. The feed pellet of claim 6, wherein the kraft pulp has a breaking length of 7.0 km or more.
 11. The feed pellet of claim 6, wherein the wood material is essentially free of bamboo.
 12. The feed pellet of claim 6, wherein the wood material consists essentially of hardwoods, softwoods, or both.
 13. The feed pellet of claim 6, wherein the wood material comprises Eucalyptus wood.
 14. The feed pellet of claim 6, wherein the wood material comprises Cryptomeria japonica wood. 